<template>
    <div class="spec-preview">
        <img :src="imgObj.imgUrl" />
        <div class="event" @mousemove="handler"></div>
        <div class="big">
            <img :src="imgObj.imgUrl" ref="big" />
        </div>
        <!-- 遮罩 -->
        <div class="mask" ref="mask"></div>
    </div>
</template>

<script>
export default {
    name: "Zoom",
    props: ["skuImageList"],
    data() {
        return {
            currentIndex: 0,
        }
    },
    computed: {
        imgObj() {
            return this.skuImageList[this.currentIndex] || {}
        },
    },
    mounted() {
        // 全局事件总线获取兄弟组件传递过来的索引值
        this.$bus.$on("getIndex", (index) => {
            // 修改当前响应式数据
            this.currentIndex = index
        })
    },
    methods: {
        handler(event) {
            let mask = this.$refs.mask
            let big = this.$refs.big
            // 盒子位置  当前鼠标距离 - mask大小 
            let left = event.offsetX - mask.offsetWidth / 2
            let top = event.offsetY - mask.offsetHeight / 2
            // 约束范围
            if (left <= 0) left = 0
            if (left >= mask.offsetWidth) left = mask.offsetWidth
            if (top <= 0) top = 0
            if (top >= mask.offsetHeight) top = mask.offsetHeight
            // 修改元素的left与top属性值
            mask.style.left = left + "px"
            mask.style.top = top + "px"
            // 修改与之对应的大图片的位置，这里位置是相反的，遮罩向右相当于图片向左
            big.style.left = -2 * left + "px"
            big.style.top = -2 * top + "px"

        },
    },
}
</script>

<style lang="less">
.spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
        width: 100%;
        height: 100%;
    }

    .event {
        width: 100%;
        height: 100%;
        position: absolute;
        top: 0;
        left: 0;
        z-index: 998;
    }

    .mask {
        width: 50%;
        height: 50%;
        background-color: rgba(0, 255, 0, 0.3);
        position: absolute;
        left: 0;
        top: 0;
        display: none;
    }

    .big {
        width: 100%;
        height: 100%;
        position: absolute;
        top: -1px;
        left: 100%;
        border: 1px solid #aaa;
        overflow: hidden;
        z-index: 998;
        display: none;
        background: white;

        img {
            width: 200%;
            max-width: 200%;
            height: 200%;
            position: absolute;
            left: 0;
            top: 0;
        }
    }

    .event:hover ~ .mask,
    .event:hover ~ .big {
        display: block;
    }
}
</style>